We present analyses of intergenerational social class mobility based on data from representative samples of the British population from 1972 to 2005. We distinguish throughout between absolute and relative rates of mobility. As regards absolute rates, we find little or no change in total mobility rates over the period covered. In the case of men, there is also little change in rates of upward and downward mobility — in contrast with the middle decades of the twentieth century when upward mobility steadily increased while downward mobility fell. This latter pattern does, however, prevail in the case of women. As regards relative rates, we again find, for men and women alike, an essential constancy over time. This, then, indicates that such changes as are apparent in absolute rates derive from shifts in class distributions rather than from any significant increase or decrease in social fluidity. Our results are contrary to the prevailing view in political and media circles that in Britain today the level of social mobility is in decline, although for men the pattern of mobility has become less favourable. We end with some remarks on policy implications.